Ink jet type printers employ a print head that consists of a reservoir of ink and a series of nozzles on a semiconductor substrate that are used to expel the ink onto a printing surface. The ink is drawn to the substrate through channels and then expelled through the nozzles. Some types of ink jet printers expel the ink by superheating a small portion of the ink with an electric nozzle resistor located in a chamber beneath the nozzle. The boiling ink forms an expanding bubble which propels a drop of ink through the nozzle and onto the printing surface. In other types of ink jet printers, piezoelectric transducers that change their dimensions in response to an electric field are used to essentially squeeze a drop of ink through the nozzle. The number, spacing, size and condition of the nozzle holes greatly influences the print quality. By carefully controlling the expulsion of the ink through the nozzles and onto a printing surface, a high quality image can be created. For color printing applications, the three primary colors of cyan, magenta and yellow are provided by ejecting ink through nozzles or holes associated with the inkwell or print head containing each of the primary colors.
Due to the limited life span of the ink jet nozzles and other components of an ink jet print head cartridge, the print head cartridges are generally designed to be disposable. However, in recent years, a growing number of ink jet users have started having their empty ink jet print head cartridges refilled by a third party. This practice has resulted in poor print quality and may lead to a much shorter printer life span.
Inks formulated by the printer manufacturer or its affiliates have undergone extensive testing and analysis. The inks are designed and manufactured to produce the highest possible print quality with the least amount of corrosion to the internal printer components. Refilling an expended ink jet print head cartridge with an untested ink may result in poor print quality for several reasons. First, the nozzles begin to wear out and become clogged after what is basically a set number of fires. Continually refilling the ink jet print head with ink results in an ever increasing number of ineffective or unfiring nozzles. When even a few nozzles fail to fire, the degradation of output print quality is quite evident. The combination of exceeding the nozzle plate life and using inferior inks that clog the nozzles more readily than manufacturer's inks results in an unacceptable number of clogged nozzles and poor print quality. In addition, the manufacturer's printer driver color tables are set up specifically for the manufacturer's inks. Thus, even a slight change in the hue of even one ink can have a drastic effect on print quality. The manufacturer's inks are also made to have a certain density and cohesion so they will blend correctly on all paper types. By using a third party's ink, the print dots will blend unpredictably, resulting in banding, running and smearing. Finally, refilling an ink jet print head cartridge designed to be disposable with a third party's inks may result in a shorter life span for some of the ink jet printer's hardware. Some untested inks are caustic to internal printer components that come into contact with the ink. The maintenance station and the maintenance station wiper come into direct contact with the ink and, thus, can become permanently damaged by the use of inferior inks. If the maintenance station does become damaged by using these inks, the nozzle plate will not be properly cleaned. This will result in poor print quality in all future printouts, even if a new print head cartridge from the manufacturer is subsequently used.
Many consumers assume that it must be all right to have their ink jet print head cartridges refilled because the refilling tools and service are so readily available. Thus, when the printer becomes damaged and malfunctions as a result of using a refilled ink cartridge, the consumer is often just as likely to blame to the manufacturer as they are to blame the refilled ink jet print head cartridge. Thus, the manufacturer's reputation may be undesirably damaged by the third party's actions.
In some applications, it may even be desirable to disable an ink jet print head before the nozzles or the print quality degrades. For example, certain ink jet print heads may be used in postal metering situations were it is desirable to limit the number of times a particular ink jet cartridge can be used. As a further example, an ink jet printer could be rented to a user for a specified amount of time or number of uses. When the specified number of uses is exceeded, the ink jet print head needs to be disabled to prevent the user from printing extra copies.
Therefore, there is a need for an efficient, inexpensive method and apparatus for disabling the refill of expired ink jet print head cartridges. The method and apparatus should provide a way to determine when an ink jet print head has reached the end of its useful life. When this determination is made, the ink jet print head cartridge should be permanently disabled. In addition, the method and apparatus is preferably self-contained in the ink cartridge so that the technology is backwards compatible with older ink jet printers without substantially modifying the print carriage.